The present invention relates to an acceleration/angular velocity sensor unit capable of sensing an acceleration and an angular velocity.
The acceleration/angular velocity sensor unit provides a unit in which the acceleration sensor and the angular velocity sensor are packaged on a substrate and arranged in a small space.
A known acceleration/angular velocity sensor unit is satisfactory in practical use if just the dedicated sensor is incorporated into such unit. For instance, the acceleration sensor or the speed sensor is incorporated if the system is the navigation system, the acceleration sensor for sensing the acceleration in the lateral direction, or the like is incorporated if the system is the sideslip control system, and the steering angle sensor, the angular velocity sensor, or the like is incorporated if the system is the cruise control system.
FIGS. 7A to 7C are block diagrams of the navigation system, the sideslip control system, and the cruise control system in the prior art.
In FIG.7A, a navigation system 210 provides an angular velocity sensor 211 and a speed sensor 212 for the vehicle, and calculates an estimate navigation position based on information from the angular velocity sensor 211 and the speed sensor 212, then calculates a map matching position from the estimate navigation position, GPS (Global Positioning System) information, and map data information, and then displays this map matching position on a monitor screen, or the like.
In FIG.7B, a sideslip control system 220 provides a lateral acceleration sensor 221, a wheel speed sensor 222, a steering angle sensor 223, and an angular velocity sensor 224 for the vehicle, and calculates a target angular velocity from information of the lateral acceleration sensor 221, the wheel speed sensor 222, and the steering angle sensor 223, then calculates an amount of discrepancy between this target angular velocity and information of the angular velocity sensor 224, and then actuates an actuator 225 based on this amount of discrepancy.
In FIG. 7C, an adaptive cruise control system 230 provides a wheel speed sensor 231, a steering angle sensor 232, an angular velocity sensor 233, and a radar 234 to the vehicle, then catches up to a preceding vehicle based on information of the angular velocity sensor 233, and the radar 234, then calculates a controlled amount from a distance to the preceding vehicle and information of the wheel speed sensor 231 and the steering angle sensor 232, and then actuates an actuator 235 based on this calculated amount.
However, the dedicated sensors are provided individually to the navigation system 210, the sideslip control system 220, and the adaptive cruise control system 230 respectively. For this reason, a sensor having the same function, for example, the angular velocity sensor 211, the angular velocity sensor 224, and the angular velocity sensor 233 provided to three systems 210 to 230 respectively, and thus is present in plural in the vehicle. Therefore, there is a drawback with this known design that the installation of respective systems 210 to 230 into the vehicle becomes complicated.
For instance, when the failure diagnosis of the sensors in respective systems 210 to 230 is taken into consideration, such failure diagnosis must be applied individually to respective systems 210 to 230. Therefore, a problem exists that the failure diagnosis of the sensors becomes difficult.
In other words, it is desired that a plurality of sensors should be integrated into one unit and the unit should be used commonly in plural systems.
As such acceleration/angular velocity sensor unit, a unit in which a plurality of acceleration sensors are mounted on the substrate is known. Such a device is disclosed, for example in JP-A-2000-314744 (page 8, FIG. 5).
FIG. 8 herein is a reproduction of FIG. 56 of JP-A-2000-314744 in which the reference numbers are modified explaining a basic configuration of the sensor unit in the prior art. An acceleration/angular velocity sensor unit 200 is constructed by mounting a sensor substrate 202 on a base 201, then arranging multilayer piezoelectric elements 203 as a plurality of sensors on the sensor substrate 202, and arranging multilayer piezoelectric elements 204 as a plurality of sensors on the sensor substrate 202 in orthogonal to these multilayer piezoelectric elements 203. A signal processing substrate 205 is placed on the sensor substrate 202 and the plurality of multilayer piezoelectric elements 203, 204, and then elements 206 such as resistors, capacitors, Ics, and the like are arranged on the signal processing substrate 205, and a cover 208 is put on the base 201.
However, in the acceleration/angular velocity sensor unit 200, a plurality of multilayer piezoelectric elements 203, 204 are arranged on the sensor substrate 202 and also the elements 206 are arranged on the signal processing substrate 205. Therefore, for example, the multilayer piezoelectric elements 203, 204 and the elements 206 are different in size and thus a balance of the packaging density between the sensor substrate 202 and the signal processing substrate 205 is lost. As a result, there is such a problem that the worsening of the packaging density on the sensor substrate 202 or the signal processing substrate 205 is brought about.
Also, in the acceleration/angular velocity sensor unit, the multilayer piezoelectric elements 203 as a plurality of sensors are arranged on the sensor substrate 202 and then simply the multilayer piezoelectric elements 204 are arranged on the sensor substrate 202 to intersect orthogonally with the multilayer piezoelectric elements 203. Therefore, sometimes the related sensors are packaged mutually at a distance, for example. Also, there is such a problem that reduction in a packaging precision due to the influence of bowing of the substrate, etc. is brought about.
In other words, the acceleration/angular velocity sensor unit that makes it possible to improve the packaging density and also improve the packaging precision is desired.